Propriedades estruturais, mecânicas, eletrônicas e vibracionais de novas nanoestruturas baseadas em adamantano

Abstract

This dissertation presents a study of structural, mechanical, electronic and vibrational properties of nanowires, nanoplans and nanotubes based on adamantane. For these structures, geometry optimizations were performed using two different methods: density functional theory in generalized gradient approximation (GGA) with exchange-correlation functional of Perdew, Burke and Ernzerhof (PBE) [1, 2] and the local density approximation (LDA) with exchange-correlation functional of Perdew-Wang (PWC) [1]. From the optimization of these structures, it was possible to calculate properties such as total energy, formation energy, energy gap, band structure and density of states, using the programs Dmol3, Castep and DFTB+. The results show that different symmetries can be obtained for each nanostructure and they preserve the bond lengths of adamantane’s molecule (in the case of nanotubes as we increase the radius). We also observed that the longitudinal Young’s modulus is always larger than the cross. For the thermodynamic stability, we have that the first results show that all structures can exist at room temperature. For the electronic properties, we have that gap from semiconductor to insulating. With respect to the vibrational properties so that each one of them has a particular signature in the IR and Raman spectra, and thus can be differentiated from each other, however, they also carry in your signature characteristic’s peaks corresponding to the adamantane.